1. Field of the Invention
The present invention generally relates to polyesters and more particularly relates to an improved method of making polyesters, while utilizing an eutectic mixture of diols.
2. Prior Art
Industrial quantities of polyesters are manufactured utilizing normally solid diols, that is diols which are solid at ambient temperature. Such diols include neopentyl glycol, trimethyl pentanediol, cyclohexane dimethanol, and 1,6 hexanediol. Some industrial techniques consume large quantities of energy in maintaining the solid diols in the liquid state so that they can be pumped into the reactor and react with the polycarboxylic acids to form the desired esters and polymerize to polyesters. However, it is difficult, time consuming and expensive to physically transfer waxy, solid diol to a reactor by hand. 1,6 hexanediol can be handled in drums, but it must be melted to use. During the melting, much heat is lost. When the diol is finally melted, it must be used immediately in order to avoid a further heat expenditure. Sometimes solid diol is dissolved in water to form an aqueous solution. However, the added energy needed to evaporate the water and the necessity for stainless steel storage containers and associated piping make this modification less than satisfactory.
In view of the very large quantities of waxy, solid diols which are being used to manufacture a wide variety of products including films, clothing, etc., and further in view of the current need to conserve energy because of fuel shortages and pollution which results from fuel conversion for energy purposes, it would be highly desirable to provide an improved method of handling solid diols. Such method should be less expensive, utilize less energy, and facilitate the storage, transportation and use of the polyester-making components. Such method should also be capable of reducing the overall time necessary for charging the components into the reactor.